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This invention is in the field of non-intrusively analyzing variations or changes in the different scattering mediums within a non-homogeneous body, by the use of collimated light pulse with a pre-determined pulse duration to illuminate the mediums and by detection of the varying scattering effects on the light produced by the variations in the mediums scattering characteristics.
There exist many systems using collimated light from a laser source to illuminate a subject and then by analyzing the light as affected by subject, to determine one or several properties or characteristics of the subject. For example, as shown in U.S. Pat. No. 5,995,866, a short pulse of laser radiation is directed at a subject, which may be tissues, liquids, gases, or solid particles in a suspension, and light reflected or scattered from the subject is scanned by an electro-optical imaging means to generate image signals. Light from the subject causing variable fluorescence or spectral radiation, is detected as varying signals which are processed to detect cancerous cells, to quantize the cells as to number, shape or distribution, and to the stage of development.
U.S. Pat. No. 6,205,353 uses a group of sources of light at different wavelengths and detectors to generate a plurality of time resolved intensity data of back-scattered light from a highly scattered turbid medium and a reconstruction algorithm to reconstruct an image of the medium.
U.S. Pat. No. 5,949,077 shows how cancerous tissue within healthy tissue may be illuminated with collimated light from a laser source so the portion of the light transmitted though the cancerous tissue is captured as a shadow due to the varying absorption and scattering properties of the cancerous tissue relative to the healthy tissue. In the disclosed system, a light wavelength is chosen so an image is formed from the luminescent light from the subject and the light scattered by the scattering medium.
U.S. Pat. No. 5,813,988 uses a laser light source to illuminate a highly scattering turbid medium with a pulse of light. Light from the medium is received by a plurality of intersecting source/detecting sets in combination with time resolving equipment to produce a number of time-resolved intensity curves for the diffusive component of the light emerging from the medium over a relatively long period of time. Each of curves is processed according to an inverse reconstruction algorithm to form an image of the subject.
U.S. Pat. No. 5,140,463 discloses a system for improving the signal to noise ratio of an image signal produced by directing collimated light to an image hidden within a highly scattering semi opaque disordered medium by using space gated imaging or time gated imaging.
U.S. Pat. No. 5,799,656 produces an image of a subject located in or behind a turbid media, such as for example, in the cancer screening of breasts. It utilizes a special property of calcification in breast tissues that are suggestive of cancers and which can be discovered using optical imaging, with time and space gating of the light emerging from the illuminated medium.
U.S. Pat. No. 5,735,276 is similar to U.S. Pat. No. 5,995,866 in its use of collimated light and computer analysis of reflected and fluorescent light from the illuminated subject.
In addition to the patented systems described above, other methods and systems have attempted to use light in different diagnostic methodologies because of its low cost and its non-intrusive and non-ionizing radiation effects. While short pulse lasers were used, the focus of these systems was on analysis of the effect of the subject or probed material on the long term or diffusive component of emerging light or steady state light transmitted through the illuminated material or on the effect of the subject or probed material on the light altered by the transmittance characteristics of the subject material. A disadvantage of these systems is the derived transmittance signal lacks a direct precise correlation between the property of the light illuminating the subject scattering and absorbing medium, for example a tumor, with different transmittance characteristics relative to its surrounding normal tissue, and the different effects or the varying effects on the radiated light produced by the related varying characteristics of the tumor and normal tissue, requiring a complex inverse analysis algorithm to reconstruct the Image.
In the case of scattered or reflected light, relative to the incident light, the temporal profile of the different reflectance signals produced by the different effects of materials with varying scattering characteristics such as a tumor inclusion, and the surrounding medium such as normal tissue, on the light radiation, can be correlated with the spatial distribution of the inclusion. However, there is no capability for processing the reflected signal received from scattering mediums and comprised substantially of the ballistic light photons, traversing the shortest path and carrying the most information, about the scattering mediums, for example a tumor within healthy tissue, with the varying reflectance characteristics of the mediums.
While short pulse width lasers have been used in an attempt to detect enclosed or materials surrounded by partially opaque or turbid mediums, such as a tumor within healthy tissue, the short pulse width laser has not been used in a way that optimizes the recovery of information from the directly reflected signal and provides a detectable signal capable of producing more accurate and precise information at small material sizes, such as the initial growth stages of a cancerous tumor in healthy tissue.
This invention overcomes the disadvantages of prior art systems that use radiation, such as collimated light from a laser to illuminate a non-homogeneous body, comprising materials with varying light reflectance or transmission or scattering, characteristics, relative to each of the other materials, for producing data indicative of the size, location or image, of the materials enclosed or hidden by the scattering turbid medium of another of the non-homogeneous body""s materials. This invention overcomes the prior art systems"" disadvantages by illuminating the materials with a radiation pulse having a temporal pulse width minimized, relative to a combined factor tp* related to the materials absorption coefficient and speed of propagation for the radiation.
Accordingly, it is an object of this invention, to detect the presence of at least one subject material or subject body or probed body located within or hidden or enclosed by another enclosing material or hiding material, and where the materials are of varying or different light scattering or reflective characteristics so the variations produced by the varying scattering mediums of the respective materials on the radiation, may be detected, analyzed or processed to produce at least one indicator comprising data or displays of the location or size or image, or other measurable indicia of the materials.
It is another object of this invention, to increase the accuracy and precision of the of the reflected signals in detecting an enclosed subject material, enclosed or hidden from the source of radiation, by an enclosing material or layer of material, between the subject material and the source of radiation, by selecting a temporal pulse width tp so the combined factor, tp* as described below, of the light pulse width tp, the extinction coefficient xcexa for the materials comprised by the materials in a non-homogeneous body, and the propagation speed c of the radiated light through the materials, is selected to minimize combined factor tp* or to a value no larger than about 1.
It is another object of this invention to employ a data acquisition system to receive and process perspective related reflected radiation from a non-homogeneous body and the materials within, to construct a two or three dimensional image of a material in the path of the radiation, hidden or separated from the radiation directly on the non-homogeneous body by another of the non-homogeneous body""s materials.
The inventive principles as disclosed herein is of a system and method for producing human readable information in data, for example in a visual display or in any other forms of perceptible data, relative to a non-homogeneous body comprising at least a first material enclosing or hiding a second material enclosed or hidden by the first material as for example an inclusion in a scattering turbid medium such as tissue material, where the materials are of different or varying reflectance or scattering characteristics.
By non-homogeneous body is meant a body comprising respective materials of different or varying radiation scattering characteristics. By enclosed material or hidden material or body, is means a material or body or inclusion enclosed by another material, comprised by the non-homogeneous body, enclosing or hiding the enclosed or hidden from the path of radiation and so the path of radiation is through the enclosed material or hiding material to the enclosed material or hidden material, and the path of the directly reflected radiation is from a respective incident point in the non-homogeneous material. By varying materials is meant materials having relative variations between the scattering characteristics of the radiated materials in the radiation path, for example as explained in Advances in Optical Imaging of Biomedical Media, by R. R. Alfano, S. G. Demos and S. K. Gayen, published in Annals New York Acad. Sci., 1997, Vol. 820(2), pp. 248-270, incorporated in, and made a part of, this application.
As explained in Advances in Optical Imaging of Biomedical Media, an ultra short radiation pulse, may be used to illuminate a non-homogeneous body, and an image may be constructed substantially from the reflected ballistic or coherently scattered photons reflected from the varying or different scattering mediums within the body and which traverse the shortest path, carrying significant information about the materials in the radiation path.
In accordance with the description of a preferred embodiment and the principles of the disclosed invention, as describe herein, by temporal pulse width, is meant a pulse width tp measured in time relative to a combined factor tp*, as explained below and selected to minimize the value of tp* or to limit tp* to a value no greater than about 1. By combined factor tp* is meant the factor tp*=xcexac tp where tp represents the pulse width, and c represents the speed of propagation of the radiation through the non-homogeneous body""s materials and xcexa represents the extinction coefficient of the materials, which is related to the materials"" absorption coefficient a and scattering coefficient "sgr", by the relationship xcexa=a+"sgr". According to the inventive principles, the pulse width tp, is selected so the combined factor tp* is minimized with respect to the materials extinction coefficientxcexa and speed of propagation, c or selected so the combined factor tp* is no greater than about 1.
As shown in a preferred embodiment, tp* is minimized or limited to a value no greater than about 1, to produce one or more indicators of selected indicia or properties of a non-homogeneous body, by detecting the directly reflected radiation from the respective incident points, as explained below, for example on the interface between an enclosing or hiding material and an enclosed material, such as an inclusion, with different or varying scattering characteristics, relative to each other, as explained herein, and which serves to prevent masking of the material by multiple scattering of photons reflected from the materials and to reveal with precision the details of a subject body within the enclosing material.
As would be apparent to those skilled in the art, the varying materials may not be fully enclosed or enclosing but arranged in layers so the material of interest such as an inclusion, is separated from the source of radiation by another of materials. By interface is meant the boundary between materials with varying scattering characteristics which produces variations in the reflected light, from the incident points on the radiation path. By incident points is meant the respective points in the non-homogeneous body along the radiation path from which the radiation is reflected directly back, for example through an enclosing material through an interface to an enclosing material, through enclosing material to the enclosing material on the other side or back side of the enclosed material and which respectively reflect the radiation, according to the respective scattering characteristics of the respective enclosing and enclosed materials.
By indicator is meant one or more indications of any measurable indicia for the material or materials of the non-homogeneous body derived in any way from perceptible data detected and acquired responsive to the reflected light from the incident points, from any system or method now or hereafter in existence.
According to the disclose inventive principles, what is shown is a system and method for optical imaging which uses a source of radiation to radiate a non-homogeneous body, comprising a plurality of materials with varying scattering mediums, where the laser temporal pulse width tp is selected so the combined factor tp*=xcexac tp, is a minimum value or to a value no greater than about 1, where xcexa represents said extinction coefficient of said scattering mediums, and c represents the propagation speed of light radiation through the scattering mediums, and where a data detector receives the radiation reflected by respective incident points located in said radiation path, producing an indicator for at least one of the materials in the radiation path.
The radiated energy in the form of photons traveling in waves, enter the non-homogeneous body and are scattered by the varying materials, as explained above, within the non-homogeneous body and as would be know to those skilled in the art, and as explained with reference to Advances in Optical Imaging of Biomedical Media by Alfano et al., incorporated herein. Where an enclosing or hiding material has a different or varying scattering coefficient, "sgr", the reflected or scattered light varies in accordance with the variation in the materials scattering coefficients "sgr"1 and "sgr"2, respectively. At the interface, for example, between the varying materials, where there is a change in the respective material""s scattering coefficients, "sgr"1 and "sgr"2, the characteristics of the reflected light will change responsive to the relative changes in the scattering coefficients, "sgr"1 and "sgr"2, accordingly. When the reflected radiation is time resolved relative to the distance traveled of the radiation in the radiation path, the location of the interface between the first and second varying may be detected, as a change in the reflected radiation. As shown for a preferred embodiment the scattering coefficient "sgr"1 for the enclosing material comprised by the non-homogeneous body, is less than the scattering coefficient "sgr"2 for the enclosed or hidden material comprised by the non-homogeneous body.
By detecting and resolving the reflected radiation with respect to time, the changes in the reflected radiation produced by incident points at the interface for example, or at any other location in the non-homogeneous body, may be analyzed to produce an indicator of the size, location or image of the interface or other materials or locations of interest in the non-homogeneous body.
As would be apparent to those skilled in the art, the disclosed invention is not limited but may be applied to the imaging of any non-homogeneous body comprising materials with relative varying scattering characteristics and may be used with detector or data acquisition systems now or hereafter in existence which would be capable of detecting the reflected light and producing perceptible data for an indicator of the size, location or image or other indicia of at least one of the materials.
These and other objects and advantages of the disclosed invention shown in a preferred embodiment according to the inventive principles, will become apparent to those skilled in the art upon reading the following Description of the Preferred Embodiment.